This section is from the book "A Practical Treatise On The Joints Made And Used By Builders", by Wyvill J. Christy. Also available from Amazon: Practical treatise on the joints made and used by builders.
Astragal Joint is a copper-bit joint ornamented with one or more astragals. An astragal is a small moulding of semi-circular profile, and, amongst other uses, was employed by the ancients to mark the division between the capital and shaft of a column, but it is questionable to which of these members it really belongs. Its position, however, there and elsewhere, sometimes gives the idea that it was used to conceal a joint, and plumbers appear to have wisely adopted it for a somewhat similar purpose. When attached to round pipes astragals are formed either by dividing a small pipe longitudinally into halves, or else by casting them in moulds, and in either case they are bent round the enlarged or female end of the pipe, and neatly soldered on with the copper-bit and fine solder. When the socket happens to be cast, it is usual to cast it complete with astragals and ears.
Autogenous Soldered Joint is made without solder by merely scraping or cleaning, and fusing by means of a blowpipe and a mixture of hydrogen gas and air, or other appropriate gas, the edges to be united, which are placed sufficiently close to run together, otherwise a stick of the metal must be fused at the same time and allowed to drop upon them. It is useless in plumbers' roof work, because the intense heat required to melt lead would be followed by an amount of coolness and contraction that would inevitably produce cracks in proximity to the joint, having regard to the friction between the lead and the underlying surface.
Great care is necessary in bedding w.c. trunks, basins, soil-pipes, traps, etc, so that there may be no settlement to cause lower parts to receive support from upper ones, and then when the strain is too great to break or draw away from them at weak sections or imperfect joints. Though not falling within the plumbers' domain, it may be here observed that in bedding soil pipes, in that part of their course from the inside to the outside of a building which passes through the wall, it is essential that their position should be such as to enable the joints to be reached at every part, and where stoneware pipes are used the same precaution is necessary throughout their whole downward course. Where the drain-pipe is not ventilated, as is unfortunately too frequently the case, it is obvious that no joint can be pronounced secure against the passage of mephitic vapour unless absolutely and unalterably non-porous, and certainly neither clay nor cement can be so styled. In some instances lead soil-pipe is joined on to a stoneware socket system, in which case the junction, after being made with yarn and clay in the usual manner, may be top coated with a mixture of resin and tallow, described under Cement Joint, to the depth of half an inch or thereabouts.
Block Joint is a mode of connecting lengths of vertical lead soil or waste pipes on wood blocks about 10 feet apart, and which are usually built or let into chases left in the walls for the pipes. A lead flange about 5 in. larger than the diameter of the pipe, and with a central orifice a trifle larger than the pipe, is worked round a hole cut and dished in the block, as shown in Fig. 136. The lower length of the pipe is then passed up through the hole so that its funnel may be tafted back upon the flange, after which the top length is prepared by shaving, etc, and stepped into the funnel, and the whole are soldered together by wiping, as described under Wiped Joint.